The invention relates to mechanisms for moving a web or a tape in opposite directions between two spools or hubs, having mechanical brakes to prevent slack developing between the hubs; and in particular to a recording and/or reproducing apparatus for a record carrier in the form of a tape which is movable in opposite directions between two rotatable winding hubs, which apparatus comprises two winding spindles for driving the two reel hubs and two braking devices for braking the two reel hubs, which braking devices comprise brake discs which are positively connected to the winding spindles, brake bands which are adapted to engage with the brake discs, and brake levers which are movable in a plane which extends parallel to the base surfaces of the brake discs, and two ends of the brake bands, one of which is pulled and the other is pushed by the brake disc during braking, being connected to the brake levers, resilient means such as a brake spring for biasing each brake lever, under the influence of which spring the brake band is urged against the brake disc during braking, and a stop being provided for each brake lever; which stop limits the movement of the brake lever under the influence of the brake spring acting on said lever. Such an apparatus is known from German Anslegeschrift No. 20 15 582.
In such apparatus it is important to ensure that during each braking operation the record carrier which is moved between the two reel hubs remains sufficiently taut, that the record carrier windings are not slackened and that no loops are formed in the record carrier, because this may lead to incorrect operation, damaging or breakage of the record carrier during subsequent use of the apparatus. In order to obtain such a tensioning of the record carrier the braking action exerted on the hub from which the record carrier is unwound should be greater than the braking action exerted on the reel hub on which the record carrier is wound. If a record carrier is unwound from a reel with a large number of turns and a correspondingly large mass onto a reel with only a few turns and braking is effected, the braking action on the reel hub from which the record carrier is unwound should be a multiple, for example 35 to 50 times, of the braking action exerted on the reel hub onto which the record carrier is wound. Care must then be taken that the record carrier is not subjected to excessive mechanical stress during a braking operation.